Oxidative coupling of alkylphenols catalyzed by metal complexes of imino acid compounds

ABSTRACT

Carbon-carbon coupled self-condensation products obtained by the oxidative coupling of alkylphenols are prepared by contacting an aqueous mixture of an alkyl phenol with oxygen in the presence of sufficient alkaline material to sustain a pH in the range of 8.5-9.5 during the oxidative coupling reaction and a catalyst system comprising certain imino acid chelates of Cu 2 , Ni 2 , Co 2 , Ce 3 , Cr 3 , Mn 2  and Fe 3 . The mixture may optionally contain a surfactant.

FIELD OF THE INVENTION

The present invention concerns generally an improved process forpreparing self-condensation products, such as diphenoquinones,biphenols, dinaphthenoquinones and binaphthols from alkylphenols,alkoxyphenols and naphthols and to a catalyst composition for use insaid process. More particularly, the invention concerns a method ofpreparing carbon-carbon coupled condensation products of alkylphenols,alkoxyphenols or 1-naphthols by contacting an aqueous mixture of thephenol or naphthol with oxygen or an oxygen-containing gas optionally inthe presence of a surfactant and sufficient alkaline material to sustaina pH in the range of 8.5-9.5 during the oxidative coupling reaction anda catalyst system comprising an imino acid chelate of Cu², Ni², Co²,Ce³, Cr³, Mn² or Fe³ wherein the imino acid has the formula

    R-N[CH.sub.2).sub.n CO.sub.2 H] .sub.2

wherein n is 1 or 2 and R is hydrogen, alkyl, hydroxy alkyl, oxaalkyl,cycloalkyl, aryl, pyridyl or --(CH₂)_(n) CO₂ H wherein n is 1 or 2.

DESCRIPTION OF THE PRIOR ART

It is well known in the art that substituted phenols can be oxidized toyield self-condensation products, including diphenoquinones, biphenolsand polyphenoxy ethers. The procedure employed in the preparation ofthese derivatives is generally referred to as the oxidative coupling ofphenols.

The self-condensation products resulting from these oxidative couplingreactions can be catagorized as either the result of carbon-carboncoupling or carbon-oxygen coupling of said phenols. Diphenoquinones andbiphenols are prepared by carbon-carbon coupling in accordance with thefollowing general reactions depending upon the reactive sites availablein the phenol employed. ##STR1## wherein R is hydrogen or R₁ and whereinR₁ is either alkyl, alkoxy, or another substitutent all of which arewell known in the art.

Similar, polyphenoxy ethers are prepared by carbon-oxygen coupling inaccordance with reactions such as the following general reaction:##STR2## wherein R and R₁ are as defined above and n is an integer.

A variety of materials, including metals and various salts and complexesthereof, have previously been disclosed as useful in promoting theoxidative coupling of alkylphenols. Thus, U.S. Pat. No. 2,785,188,discloses that copper powder may be utilized to prepare diphenoquinonesfrom 2,6-dialkyl-4-halophenols. Similarly, various copper salts andcombinations or complexes prepared from copper salts and a variety ofnitrogen-containing compounds have been disclosed as useful in thepreparation of both diphenoquinones and polyphenoxy ethers. Theseinclude, for example, cupric complexes of primary and secondary amines(U.S. Pat. No. 3,306,874); and cupric complexes of tertiary amines (U.S.Pat. Nos. 3,306,875 and 3,134,753).

The use of manganese amine chelates as oxidizing agents in oxidativecoupling reactions is described in U.S. Pat. No. 3,825,521.

A variety of basic compounds have also been employed in oxidativecoupling reactions. In many of these, such as those disclosed in U.S.Pat. Nos. 2,905,674, and 2,785,188, the function of the alkalinematerial was to react with an acidic component, such as HCl, liberatedduring the course of the reaction and, therefore, a stoichiometricamount of the base was used.

It should be noted that, previous methods of preparing coupled productsfrom alkyl- or alkoxy-phenols have required the use of either organicsolvents or stoichiometric amounts of organic oxidizing reagents. Thepresent invention provides for a metal imino acid complex catalystsystem useful in the preparation of carbon-carbon coupled phenols ornaphthols in an aqueous reaction medium. Also, with most of the priorart systems the resulting product or products were determined by theparticular catalyst employed and could not easily be controlled. Thepresent invention provides for a system which can be readily modified toproduce either the biphenol or diphenoquinone directly from the reactionmixture.

It has also been found that the type of product which is produced can becontrolled by the amount of alkaline material and by the amount ofcatalyst employed in the catalyst system. By comparison, the prior artcatalysts and processes employing said catalysts have a number ofdisadvantages which have restricted the utility of said catalysts andprocesses. These include (a) the requirement that the reaction beconducted in an organic solvent, (b) the fact that the primary productproduced is often the polyphenoxy ether, and (c) the inability to formthe biphenol, bisphenol and binaphthol derivative directly and insubstantial quantities without requiring that this material be producedby a subsequent hydrogenation of the diphenoquinone, stilbenequinone ordinaphthenoquinone prepared in the oxidative coupling reaction. Thesedisadvantages have been overcome by the use of the catalyst and processof the present invention as is described in detail hereinafter.

In accordance with the present invention, there is provided a method ofpreparing a condensation product of an "alkylphenol", an "alkoxyphenol"or a "1-naphthol", by an oxidative coupling reaction said methodcomprising contacting an aqueous mixture of the phenol or naphthol withoxygen or oxygen containing gas in the presence of sufficient amount ofalkaline material to sustain pH in the range of about 8.5-9.5 during theoxidative coupling reaction and a catalyst system comprising an iminoacid metal complex wherein the metal source is selected from the classof divalent copper, nickel, cobalt and manganese and trivalent cerium,chromium and iron; and wherein the imino acid has the formula:

    R-N[CH.sub.2).sub.n CO.sub.2 H].sub.2

wherein n is 1 or 2 and R is hydrogen, alkyl, oxaalkyl, hydroxy alkyl,cycloalkyl, aryl, pyridyl, or --(CH₂)_(n) CO₂ H wherein n is 1 or 2. Ina preferred embodiment the aqueous mixtures additionally contains asurfactant. The phenols or naphthols, metal complexes, and alkalinematerials which may be utilized are critical to the present inventionand are described in detail below.

Phenols/Naphthols

The phenols which may be employed in carrying out the present inventioninclude both alkylphenols and alkoxyphenols. Specific phenols which maybe utilized are described in detail below.

The alkylphenols which may be utilized are defined as any alkylphenolhaving at least two alkyl substituents, with the proviso that thephenols which have only two alkyl substituents must have thesubstituents in the ortho, ortho(2,6 in the formula below) or ortho,para (2,4 in the formula below) positions. These phenols are frequentlyreferred to by the position of the alkyl sustituent or substituents onthe benzene ring as set forth in the following formula: ##STR3##

The process of the invention is applicable to any alkyl phenol having atleast two alkyl substituents and steric properties such as to permit acoupling reaction. Thus if the para position is substituted with analkyl group other than a methyl group, at least one ortho position mustbe unsubstituted. If one ortho and the para position are substituted, atleast one of those substitutions must be a tertiary alkyl group. If bothortho positions are substituted, the para position must be eitherunsubstituted or substituted with a methyl group and no more than onemeta position may be substituted with a tertiary alkyl group.

Thus, the alkylphenols will have one of the following formulas: ##STR4##wherein R₂ and R₆ are alkyl and R₃, and R₅ are hydrogen or alkyl, and R₄is hydrogen or methyl with the proviso that R₃ and R₅ cannot both betertiary alkyl. ##STR5## wherein R₂ and R₄ are alkyl provided that atleast one of said alkyl groups is a tertiary alkyl and R₃ and R₅ arehydrogen or alkyl.

As used herein, the term alkyl refers to any monovalent radical derivedfrom a saturated aliphatic hydrocarbon by removal of one hydrogen atomtherefrom. The term includes both straight chain and branched chainmaterials containing from 1 to about 12 carbon atoms. Preferred resultsare achieved with alkylphenols wherein the alkyl substituent containsfrom 1 to about 5 carbon atoms.

The alkyl substituents are referred to herein as primary, secondary ortertiary alkyl depending upon the greatest number of carbon atomsattached to any single carbon atom in the chain.

Condensation products of any alkylphenol coming within theabove-mentioned definition may be prepared in accordance with thepresent invention. As is apparent from that definition, the alkylphenolsinclude dialkylphenols, trialkylphenols, and tetraalkylphenols.Specifically, the phenols which may be utilized include the following:

Ortho, para-substituted phenols including 2,4-dialkylphenols,2,3,4-trialkylphenols, 2,4,5-trialkylphenols, and2,3,4,5-tetraalkylphenols wherein the alkyl groups are either methyl ora primary, secondary, or tertiary alkyl provided that at least one ofthe alkyl groups in either the 2 or the 4 position is a tertiary alkyl,and ortho, ortho-substituted phenols including 2,6-dialkylphenols,2,3,6-trialkylphenols and 2,3,5,6-tetraalkylphenols wherein the alkylgroups are either methyl or a primary, secondary, or tertiary alkylprovided that in the case of 2,3,5,6-tetraalkylphenols at least one ofthe alkyl groups in either the 3 or the 5 position is either a primaryor secondary alkyl.

Representative ortho, para-substituted phenols which may be usedinclude, for example 2,4-ditertiary-butylphenol,2-methyl-4-tertiary-butylphenol, 2,-tertiary-butyl-4-methylphenol,2,4-ditertiary-amylphenol, 2,4-ditertiary-hexylphenol,2-isopropyl-4-tertiary-butylphenol,2-secondary-butyl-4-tertiary-butylphenol,2-tertiary-butyl-3-ethyl-4-methylphenol,2,5-dimethyl-4-tertiary-butylphenol, and2-methyl-3-ethyl-4-tertiary-butylphenol.

Representative 2,6-dialkylphenols (ortho, ortho-substituted) include,for example 2,6-xylenol, 2-methyl-6-butylphenol, 2,6-diisobutylphenol,2-octyl-6-methylphenol, 2-isobutyl-6-dodecylphenol,2,6-ditertiary-butylphenol, 2,6-ditertiary-hexylphenol,2-ethyl-6-methylphenol, 2-methyl-6-tertiary-butylphenol,2,6-diisopropylphenol, 2,6-di-secondary-butylphenol, and2-cyclohexyl-6-methylphenol.

Representative 2,3,6-trialkylphenols which may be utilized in accordancewith the present invention include, for example, 2,3,6-trimethylphenol,2,3,6-triethylphenol, 2,6-dimethyl-3-ethylphenol,2,3-diethyl-6-tertiary-butylphenol, and2,6-ditertiarybutyl-3-methylphenol.

Representative 2,3,5,6-tetraalkylphenols which may be utilized inaccordance with the present invention include, for example,2,3,5,6-tetramethylphenol, 2,3,5,-trimethyl-6-tertiary-butylphenol,2,6-ditertiary-butyl-3,5-dimethylphenol,2,3,6-trimethyl-5-tertiary-butylphenol, 2,3-dimethyl-5,6-diethylphenol,and 2-methyl-3-ethyl-5-isopropyl-6-butylphenol.

When an ortho, para substituted alkylphenol is employed the couplingreaction proceeds in accordance with the following reaction resulting inthe o, o'-coupled product. ##STR6## In this reaction each R representshydrogen or an alkyl group as defined above depending upon whether di-,tri-, or tetra-substituted alkylphenol is utilized.

Similarly, with the ortho, ortho-substituted alkylphenols, the reactionresults in the p,p'-coupled product in accordance with the followingreaction wherein R is hydrogen or alkyl depending upon which of theabove-mentioned alkylphenols is used as the starting material. ##STR7##

It has also been found that alkoxyphenols may be oxidatively coupled inaccordance with the present invention. These include among others2,6-disubstituted phenols wherein at least one of the substituents is analkoxy group containing up to about six carbon atoms such as methoxy,ethoxy, propoxy, butoxy and pentoxy. In addition to the2,6-dialkoxyphenols, 2-alkyl-6-alkoxyphenols, wherein the alkyl groupsare as defined above for the alkylphenols, may be utilized. As usedherein the term alkoxyphenols is intended to include both types ofcompounds. These compounds may be represented by the following generalformulas: ##STR8## wherein each R is any alkyl group as defined abovefor the alkylphenols or OR and R₁ is either hydrogen or methyl, providedthat the substituents adjacent to R₁ cannot both be tertiary alkyl ortertiary alkoxy. Representative alkoxyphenols which may be utilizedinclude, for example, 2,6-dimethoxyphenol, 2,6-diethoxyphenol,2,6-dibutoxyphenol, 2-methoxy-6-pentoxyphenyl, 2-methyl-6-methoxyphenoland 2-ethyl-6-propoxyphenol, 2-methoxy-3-ethoxy-6 methylphenol.

When these phenols are utilized the reaction proceeds in accordance withthe following representative reaction resulting in the p,p'-coupledmaterial. ##STR9##

Mixtures of 2 different phenols may also be utilized. When this is done,there generally results a mixture of three different materials. Two ofthese are the products of the oxidative coupling of one molecule of oneof the phenols with a second molecule of the same phenol. The thirdproduct is that resulting from the oxidative coupling of one molecule ofthe first phenol with one molecule of the second phenol. The productsmay be separated prior to use, as is well understood in the art.

Moreover, 1-naphthol and substituted 1-naphthols having at least 1unsubstituted position ortho or para to the hydroxyl group may also beemployed. The naphthols which may be coupled in accordance with thepresent invention are represented by the following general formula:##STR10## wherein R₂, R₃ and R₄ are hydrogen, alkyl containing from 1 to5 carbon atoms, or alkoxy containing from 1 to 6 carbon atoms, providedthat either or both R₂ or R₄ are hydrogen and R₅, R₆, R₇, and R₈ arehydrogen, alkyl containing from 1 to 5 carbon atoms or alkoxy containingfrom 1 to 6 carbon atoms provided that tertiary alkyl or tertiary alkoxygroups may not be attached to adjacent carbon atoms of the naphthalenemolecule.

Representative naphthols which may be utilized include, for example,1-naphthol, 2-methyl-1-naphthol, 2,3-dimethyl-1-naphthol,4-ethyl-1-naphthol, and 2-methoxy-1-naphthol.

When a naphthol is employed, the coupling reaction takes place inaccordance with the following general reactions depending upon thereactive positions -- i.e., those either ortho or para to the hydroxygroup -- available. Thus, if R₂ is hydrogen and R₄ is alkyl or alkoxy##STR11## Similarly, if R₄ is hydrogen and R₂ is alkyl or alkoxy, theproducts are the 4,4'-binaphthol and the 4,4'-dinaphthenoquinone. Whenboth R₂ and R₄ are hydrogen the products may be a mixture of the 2,2'-;2,4'- and 4,4'-binaphthols and dinaphthenoquinones.

Finally, the catalyst system of this invention may also be employed toprepare coupled products of alkylphenols wherein all of the positionsortho and para to the hydroxy group are substituted and the substituentpara to the hydroxy group is methyl. These alkylphenols may berepresented by the following general formula: ##STR12## wherein R₃ ishydrogen, a primary, secondary or tertiary alkyl or an alkoxy group:

R₅ is a primary or secondary alkyl group containing from 1-5 carbonatoms and R₂ and R₆ are a primary, secondary or tertiary alkyl or analkoxy group.

Representative compounds which may be employed include, for example,2,4,6-trimethylphenol; 2,6-di-secondary-butyl-4-methylphenol;2-methyl-6-t-butyl-4-methylphenol; and 2,3,4,6-tetramethylphenol.

When one of these alkylphenols is employed, the reaction proceeds inaccordance with the following general reaction to produce thestilbenequinone or bisphenol derivative. These materials are useful inthe same applications set forth above for the diphenoquinones,dinaphthenoquinones, biphenols and binaphthols. ##STR13## wherein thesubstituent values are those specified in formula V.

It should be specifically noted that the term "alkyl phenol" is herebydefined as only those alkyl phenols of formulas I, II and V and theirisomers, the term "alkoxy phenol" is hereby defined as only those alkoxyphenols of formula III and their isomers and that the term "1-naphthol"is defined as only those 1-naphthols of formula IV and their isomers.

Metal Complex

One of the essential components of the catalyst system of the presentinvention is a metal imino acid complex. As mentioned hereinbefore themetal source for this complex may be divalent copper, nickel, cobalt ormanganese or trivalent chromium, iron or cerium.

The imino acid compounds which may be complexed with the metal ionsource useful in achieving the improved results of the present inventionhave the following structural formula:

    R-N[(CH.sub.2).sub.n CO.sub.2 H].sub.2

wherein R is hydrogen, hydroxy alkyl, oxaalkyl, cycloalkyl, aryl,pyridyl or

    --(CH.sub.2).sub.n CO.sub.2 H

and wherein n is 1 to 2. Useful imino acids encompassed by the aboveformula include:

Hn(ch₂ co₂ h)₂ -- nitrilodiacetic acid

N(ch₂ co₂ h)₃ -- nitrilotriacetic acid

Hoch₂ ch₂ n(ch₂ co₂ h)₂ -- n-(2-hydroxyethyl)-iminodiacetic acid

N(ch₂ ch₂ co₂ h)₃ -- nitrilotripropionic acid ##STR14##p-n-butylanilinediacetic acid

In accordance with the invention the imino acid is complexed with asource of certain metal ions. These ions may be derived from thecorresponding metal salts and may include any of the following:

halides, such as chloride, bromide and iodide,

basic halo hydroxides such as for example represented by the formulaCuX₂.Cu(OH)₂ or CoX₂.CO(OH)₂ wherein X is chlorine, fluorine, bromine,or iodine,

carboxylates, such as acetate, benzoate, and butyrate

nitrates

sulfates

alkyl sulfates wherein the alkyl group is either a straight or branchedchain alkyl containing from 1 to about 20 carbon atoms including, forexample, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl,

aryl sulfonates wherein the aryl group contains at least one aromaticring which may, if desired, have alkyl substituents such as thosementioned above, attached thereto including, for example, benzene,naphthalene, dodecyl benzene, and methyl naphthalene.

carbonates,

basic carbonate -- i.e., CuCO₃.Cu(OH)₂,₂ CoCO₃.Co(OH)₂.H₂ O

hydroxides,

chlorates -- i.e., Cu(ClO₃)₂,

These complexes may be prepared in any manner and the preparationthereof has not been found to be critical to the present invention.Similarly the ratio of imino acid to metal source has been found to benot narrowly critical. It should be noted that if the ratio of iminoacid to metal source is less than one, less complex is formed. Thefollowing three methods have been employed but other methods which willbe readily apparent to those skilled in the art from the description ofthe invention given herein, may also be utilized.

First, suitable amounts of the imino acid and a source of metal ions maybe combined in a suitable medium such as water and reacted to form thecomplex. The complex is prepared by simply stirring the solution for aperiod of time. If desired, heat may be applied to accelerate formationof the complex.

Alternatively, the imino acid and the source of the metal ion may simplybe combined and added to the reaction mixture wherein the complex of theimino acid is formed. When this is done, any basic compound required toneutralize acidic by-products of the complex forming reaction is alsoadded directly to the reaction mixture.

Finally, the imino acid, the source of metal ion, and any required basiccompound may be added separately to the reaction medium and the complexformed in situ. As mentioned above, the method by which the metalcomplex is prepared has not been found to be critical to the presentinvention. However, further improved conversion results have beenachieved when the source of metal ion and the imino acid are combinedprior to addition to the reaction medium.

It should be noted that the complex formed by combining the imino acidor salt thereof with a metal ion source is referred to herein as a metalimino acid complex despite the fact that the complex contains no freeacid groups. The use of such terminology is well understood in theliterature. See for example, Bailar's Chemistry of CoordinationCompounds, Reinhold Publishing Company 1956.

The amount of metal complex employed has not been found to be narrowlycritical to the process of the present invention. However, it ispreferred to employ at least 0.02 mmol of the complex per 100 mmols ofalkylphenol. If less than this amount is used, the reaction is slowerand the yields are low. Similarly, the maximum amount of complexemployed is not generally greater than 1 mmol of the complex per 100mmols of alkylphenol. At amounts much in excess of this the cost of thecatalyst results in a uneconomic system.

Although any of the above-mentioned metal complexes may be used,improved conversion results have been achieved with the cupric complexesof nitrilodiacetic acid.

As mentioned above, an advantage of the catalyst system and of theprocess of the present invention is that the reaction can be carried outin an aqueous medium instead of an organic solvent as has been used inprior art system. However, it has not been found to be critical to thepresent invention to employ a water soluble metal complex. Thus,materials which are insoluble in water as well as those which aresoluble may be utilized.

Surfactant

The catalyst composition of the present invention may also include, asan optional component thereof, a surfactant. The presence of asurfactant moderately improves conversion results and additionallyallows easier cleaning of large reactors. A variety of surfactants alsoknown as dispersants, are well known in the art and, as used herein, theterm surfactant is intended to refer to organic compounds that containin the molecule both hydrophobic and hydrophilic groups.

Surfactants are often classified, based on the hydrophilic (waterliking) group which they contain, as either anionic, cationic, nonionic,or amphorteric. Any such surfactants may be employed in the presentinvention.

Surfactants are discussed in detail in the Encyclopedia of ChemicalTechnology, Kirk-Othmer, Second Edition Vol. 19 at pages 508-589, andany of the surfactants described therein may be utilized in the presentinvention.

The amount of surfactant employed has not been found to be critical tothe utility of the catalyst system in carrying out the improved processof the present invention. However, if the use of a surfactant isdesirable such as for example to increase the amount of carbon-carboncoupled product, there should be included in the reaction mixture atleast about 0.1 mmols of surfactant per 400 mmol of phenol or naphthol.Preferred conversion results are achieved when the amount of surfactantemployed is equal to from about 0.1 to about 0.6 mmols of surfactant per400 mmol of phenol or naphthol. Additional amounts of the surfactant maybe employed; however, the use of greater amounts of surfactant hasusually not been found to significantly increase the total yield ofproduct and it is, therefore, not generally desirable to includeadditional material in the reaction mixture.

Alkaline Material

In accordance with the present invention, an alkaline material is alsoincluded in the catalyst composition to ensure that the pH during thereaction is maintained in the range of 8.5-9.5. It has been found thatthe use of an alkaline material to raise the pH in the present systemincreases the conversion to carbon-carbon coupled products and decreasesthe conversion to carbon-oxygen coupled products. The use of such amaterial to maintain the required pH also increases the rate of theoxidative coupling reaction and decreases the amount of the metalcompound which must be utilized.

The alkaline material useful in achieving the pH of the reaction and theimproved results of the present invention is selected from the groupconsisting of alkali metal hydroxides, alkali metal carbonates, andalkali metal bicarbonates. The alkaline material may be added either asa single compound or as a mixture of compounds. Representative materialswhich may be employed include, for example, sodium hydroxide, potassiumhydroxide, lithium hydroxide, sodium carbonate, lithium carbonate,sodium bicarbonate, rubidium carbonate, rubidium hydroxide, cesiumbicarbonate, and cesium hydroxide.

The amount of alkaline material employed has not been found to benarrowly critical to the present invention as long as the required pH ismaintained. However, preferred results are achieved when the amount ofsaid material is equal to at least about 20 millimols per 100 mols ofphenol or naphthol. Smaller amounts of alkaline material will normallyresult in a reaction pH of less than 8.5 and will normally cause a lowmolar conversion of starting compound to final product. A preferred pHis from about 9. Increased amounts of alkaline material may also beutilized in carrying out the present invention. It has been found that,for a given set of reaction conditions, increasing the amount ofalkaline material increases the total conversion to carbon-carboncoupled products and the relative amount of diphenoquinone,stilbenequinone, or dinaphthenoquinone as compared to the amount ofbiphenol, bisphenol or binaphthol. Thus, by varying the amount ofalkaline material to vary the pH within the required pH range of8.5-9.5, the type of product can be controlled.

Besides the selective production of carbon-carbon coupled products, anadditional advantage of the catalyst system of the present invention isthe ability to control the type of carbon-carbon coupled productproduced. Thus, it is possible to prepare selectively eitherdiphenoquinone or biphenol, stilbenequinone, or bisphenol, ordinaphthenoquinone or binaphthol, in accordance with the presentinvention. This result is achieved by controlling the amount of alkalinematerial included in the system. Generally, as the amount of alkalinematerial is increased, the percentage of quinone derivative producedalso increases. pH values higher than those suggested resulted insignificant levels of oligomer formation. (carbon-oxygen coupledproducts.)

Reaction Conditions

As mentioned above, an advantage of the catalyst system and process ofthe present invention is that it makes it possible for the oxidativecoupling reaction to be carried out in an aqueous medium. The amount ofwater employed has not been found to be critical to the presentinvention and any amount of water which will permit the reaction mixtureto be stirred during the course of the reaction may be employed. Itshould also be noted again that it is not essential that the variouscomponents be soluble in water and the term aqueous mixture as usedherein is intended to include solutions, slurries, suspension and thelike.

The components of the reaction mixture may be combined in any suitablemanner. Thus, the phenol or naphthol, surfactant, metal complex,alkaline material and water may be combined in any order in a suitablereaction vessel. Alternatively, and in a preferred method, the phenol ornaphthol and optionally the surfactant are combined in water in asuitable reaction vessel, the mixture is stirred rapidly, preferably byutilizing a stainless steel impeller turning at 3,000-10,000 RPM and anaqueous mixture of the metal salt compound is prepared to which theamine is added followed by an aqueous solution of the alkaline material.In modifications of this procedure the metal complex may be added priorto heating or the metal complex and alkaline material may be combinedprior to addition to the reaction mixture.

The reaction mixture comprising phenol or naphthol, water, metal complexand alkaline material is contacted with a suitable oxidizing agent toconvert the phenol or naphthol to the desired product. Oxidizing agentswhich may be employed in carrying out the present invention includeoxygen either alone or as an oxygen-containing gas, such as air. Theoxygen may be introduced into the reaction mixture either directly asoxygen gas or an an oxygen-generating material such as ozone, hydrogenperoxide, or an organic peroxide. The amount of oxygen utilized shouldbe sufficient to obtain the desired conversion of the phenol or naphtholto the coupled product. To assure that sufficient oxygen is present,oxygen should be introduced into the reaction mixture continuouslyduring the course of the reaction.

The reaction conditions -- i.e., time and temperature -- employed havenot been found to be narrowly critical to the process of the presentinvention. Preferred results have been achieved when the reactionmixture is maintained at from about 80° to 90° C. during the course ofthe reaction. However, temperatures above and below this preferred rangemay be utilized. At lower temperatures the reaction rate is reduced andat temperatures below about 40° C. it is so slow as to result in anuneconomic system. When operating at atmospheric pressure, as isdesirable in some commercial operations, the practical upper limit onthe temperature is 100° C., the boiling point of the water.

If the reaction is conducted at increased oxygen pressure, the reactiontime is decreased, the total yield of coupled product is usuallyincreased, and the relative amount of quinone derivative is also usuallyincreased.

The amount of time required for completion of the reaction depends onthe temperature employed and other variables such as the pressure,concentration of phenol or naphthol and the amount of metal complex,surfactant if present, and alkaline material employed. However, it hasbeen found that, when conducted at atmospheric pressure, the reaction isusually completed in 6 hours or less.

Although, as mentioned above, the process of the present inventionresults primarily in the production of carbon-carbon coupled products,there are also sometimes included in the solids removed from thereaction mixture the following: (a) unreacted phenol or naphthol, and(b) low molecular weight polyphenoxy ether. The polyphenoxy ether andphenol or naphthol may be removed by washing the solids with a solventin which these materials are soluble, such as an aromatic hydrocarbon --e.g., toluene, benzene, or a halogenated solvent -- e.g., methylenechloride. If it is desired to separate the materials from each other andfrom the solvent, this may be done by distillation.

If the reaction results in the mixture of biphenol and diphenoquinone,bisphenol and stilbene quinone, or binaphthol and dinaphthenoquinone,these materials may be separated by any method known in the art. Anespecially convenient way of separating the materials is to stir thesolid product with a dilute aqueous solution of sodium hydroxide, whichconverts the biphenol, bisphenol or binaphthol to the sodium salt whichis usually soluble in water. The insoluble diphenoquinone, stilbenequinone or dinaphthenoquinone may then be filtered off and the biphenol,bisphenol or binaphthol recovered by adding the aqueous solution of thesodium salt thereof to a dilute solution of a strong acid such ashydrochloric acid from which the biphenol, bisphenol or binaphtholprecipitates, Alternatively, the entire product may be hydrogenated orchemically reduced and converted to only the biphenol, bisphenol orbinaphthol.

The diphenoquinones and/or biphenols as well as the binaphthols,bisphenols and dinaphthenoquinones and stilbene quinones produced inaccordance with the present invention are suitable for any of the usesof these materials which have heretofore been described in the art.Thus, the diphenoquinones and dinaphthenoquinones may be used asinhibitors of oxidation, peroxidation, polymerization and gum formationin gasolines, aldehydes, fatty oils, lubricating oils, ethers andsimilar compounds as mentioned in U.S. Pat. No. 2,905,674 issued toFilbey. The diphenoquinones may also be hydrogenated, employingconventional techniques, to yield the corresponding biphenol. Thebiphenols may be employed as stabilizers in gasoline and other petroleumproducts as described in U.S. Pat. No. 2,479,948 issued to Luten et al.They may also be utilized as intermediates in the manufacture of suchuseful products as sulfones, carbonates and epoxy resins. In order todescribe the present invention so it may be more clearly understood thefollowing examples are set forth. These examples are given primarily forthe purpose of illustration and any enumeration of detail containedtherein should not be interpreted as a limitation on the concept of thepresent invention.

EXAMPLE 1

Into a first flask there were added;

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O,

0.40 grams (2 mmols) of disodium nitrilodiacetate,

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added;0.1 grams of sodium lauryl sulfate, 200 grams of deionized water and48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino acid complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 1.82 gms ofsodium hydroxide (as 45.5 ml of 1.0 N) solution was added during thecourse of the reaction to maintain the pH of the mixture at 9. Themixture was stirred under oxygen. The oxygen flow was rapid at thebeginning to flush the system. After about 1/2 hour, oxygen flow wasreduced and maintained at a level sufficient to cause slow bubbling in abubbler attached to the top of the condenser. The temperature wascontrolled by a Therm-O-Watch temperature controller. The reactionmixture was stirred vigorously and maintained under oxygen for theprescribed reaction time of 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH3with HCl, filtered to remove the water phase. A sample of the solid wasremoved, dissolved in acetone and analyzed by gas-liquid chromatography.The analysis indicated that 99+ weight percent of the 2,6-xylenol wasconverted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 37.4 gm of product was obtained as a greensolid which contained 44 weight percent diphenoquinone and 56 weightpercent tetramethylbiphenol as determined by spectrophotometricanalysis.

EXAMPLE 2

Into a first flask there were added:

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O,

0.28 grams (1 mmol) of trisodium nitrilotriacetate,

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added;0.1 grams of sodium lauryl sulfate, 200 grams of deionized water and48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino acid complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 1.560 gms ofsodium hydroxide (as 39 ml of 1.0 N) solution was added durng the courseof the reaction to maintain the pH of the mixture at 9.0. The mixturewas stirred under oxygen. The oxygen flow was rapid at the beginning toflush the system. After about 1/2 hour, oxygen flow was reduced andmaintained at a level sufficient to cause slow bubbling in a bubblerattached to the top of the condenser. The temperature was controlled bya Therm-O-Watch. The reaction mixture was stirred vigorously andmaintained under oxygen for the prescribed reaction time of 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH3with HCl, filtered to remove the water phase, and washed twice with 200ml with water. A sample of the solid was removed, dissolved in acetoneand analyzed by gas-liquid chromatography. The analysis indicated that99+ weight percent of the 2,6-xylenol was converted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 36.4 gm of product was obtained as a greensolid which contained 37.3 weight percent diphenoquinone and 62.7 weightpercent tetramethylbiphenol as determined by spectrophotometricanalysis.

EXAMPLE 3

Into a first flask there were added:

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O,

0.55 grams (2 mmols) of trisodium nitrolotriacetate

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added;0.1 grams of sodium lauryl sulfate, 200 grams of deionized water and48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino acid complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 1.432 gms ofsodium hydroxide (as 35.8 ml of 1.0N) solution was added during thecourse of the reaction to maintain the pH of the mixture at 9. Themixture was stirred under oxygen. The oxygen flow was rapid at thebeginning to flush the system. After about 1/2 hour, oxygen flow wasreduced and maintained at a level sufficient to cause slow bubbling in abubbler attached to the top of the condenser. The temperature wascontrolled by a Therm-O-Watch. The reaction mixture was stirredvigorously and maintained under oxygen for the prescribed reaction timeof 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH3with HCl, filtered to remove the water phase, and washed twice with 200ml with water. A sample of the solid was removed, dissolved in acetoneand analyzed by gas-liquid chromatography. The analysis indicated that99+ weight percent of the 2,6-xylenol was converted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 43.7 gm of product was obtained as abrown-orange solid which contained 22 weight percent diphenoquinone and70 weight percent tetramethylbiphenol as determined byspectrophotometric analysis.

EXAMPLE 4

Into a first flask there was added;

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O,

1.10 grams (4 mmols) of trisodium nitrilotriacetate

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added;0.1 grams of sodium lauryl sulfate, 200 grams of deionized water and48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino acid complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 4.16 gms ofsodium hydroxide (as 104 ml of 1.0 N) solution was added during thecourse of the reaction to maintain the pH of the mixture at 9. Themixture was stirred under oxygen. The oxygen flow was rapid at thebeginning to flush the system. After about 1/2 hour, oxygen flow wasreduced and maintained at a level sufficient to cause slow bubbling in abubbler attached to the top of the condenser. The temperature wascontrolled by a Therm-O-Watch. The reaction mixture was stirredvigorously and maintained under oxygen for the prescribed reaction timeof 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH5with HCl, filtered to remove the water phase, and washed twice with 200ml with water. A sample of the solid was removed, dissolved in acetoneand analyzed by gas-liquid chromatography. The analysis indicated that99+ weight percent of the 2,6-xylenol was converted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 30.5 gm of product was obtained as a greensolid which contained 6.6 weight percent of diphenoquinone and 93.4weight percent tetramethylbiphenol as determined by spectrophotometricanalysis.

EXAMPLE 5

Into a first flask there was added:

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O,

36 grams (2 mmols) of N-2-hydroxyethyl iminodiacetic acid,

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added;0.1 grams of sodium lauryl sulfate, 200 grams of deionized water and48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino acid complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 1.520 gms ofsodium hydroxide (as 38 ml of 1.0 N) solution was added during thecourse of the reaction to maintain the pH of the mixture at 9. Themixture was stirred under oxygen. The oxygen flow was rapid at thebeginning to flush the system. After about 1/2 hour, oxygen flow wasreduced and maintained at a level sufficient to cause slow bubbling in abubbler attached to the top of the condenser. The temperature wascontrolled by a Therm-O-Watch. The reaction mixture was stirredvigorously and maintained under oxygen for the prescribed reaction timeof 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH3with HCl, filtered to remove the water phase, and washed twice with 200ml with water. A sample of the solid was removed, dissolved in acetoneand analyzed by gas-liquid chromatography. The analysis indicated that99+ weight percent of the 2,6-xylenol was converted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 35.8 gm of product was obtained as a darkgreen solid which contained 49.7 weight percent diphenoquinone and 50.3weight percent tetramethylbiphenol as determined by spectrophotometricanalysis.

EXAMPLE 6

Into a first flask there were added;

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O, 0.24 grams (1mmols) of nitrilotripropionic acid,

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added200 grams of deionized water and 48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino acid complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 0.640 gms ofsodium hydroxide (as 16 ml of 1.0 N) solution was added during thecourse of the reaction to maintain the pH of the mixture at 9. Themixture was stirred under oxygen. The oxygen flow was rapid at thebeginning to flush the system. After about 1/2 hour, oxygen flow wasreduced and maintained at a level sufficient to cause slow bubbling in abubbler attached to the top of the condenser. The temperature wascontrolled by a Therm-O-Watch. The reaction mixture was stirredvigorously and maintained under oxygen for the prescribed reaction timeof 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH3with HCl. filtered to remove the water phase, and washed twice with 200ml water. A sample of the solid was removed, dissolved in acetone andanalyzed by gas-liquid chromatography. The analysis indicated that 94.7weight percent of the 2,6-xylenol was converted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 30.3 gm of product was obtained as a yellowsolid which contained .66 weight percent diphenoquinone and 99. percenttetramethylbiphenol as determined by spectrophotometric analysis.

EXAMPLE 7

Into a first flask there were added;

0.4 grams (2 mmols) of cupric acetate Cu(OAc)₂.H₂ O,

0.54 grams (2 mmols) of p-n-butylanilinediacetic acid

25 grams of ion exchanged water.

Into a 500 ml creased Morton flask, fitted with a gas addition tube, acondenser, a thermometer, and a stirrer capable of operating at speedsin the range of from about 3,000 to about 10,000 rpm there were added;0.1 grams of sodium lauryl sulfate, 200 grams of deionized water and48.8 grams (400 mmols) of 2,6-xylenol.

To the resulting slurry which was stirred using a Labline cruciformstainless steel impeller turning at about 6,000 rpm there was added thestirred copper imino complex solution prepared above. The resultingmixture was stirred for 15 minutes and heated to 80° C. 1.440 gms ofsodium hydroxide (as 36 ml of 1.0 N) solution was added during thecourse of the reaction to maintain the pH of the mixture at 9. Themixture was stirred under oxygen. The oxygen flow was rapid at thebeginning to flush the system. After about 1/2 hour, oxygen flow wasreduced and maintained at a level sufficient to cause slow bubbling in abubbler attached to the top of the condenser. The temperature wascontrolled by a Therm-O-Watch. The reaction mixture was stirredvigorously and maintained under oxygen for the prescribed reaction timeof 6 hours.

Product Isolation

The reaction slurry was cooled to room temperature, acidified to pH3with HCl, filtered to remove the water phase, and washed twice with 200ml with water. A sample of the solid was removed, dissolved in acetoneand analyzed by gas-liquid chromatography. The analysis indicated that99+ weight percent of the 2,6-xylenol was unreacted.

The solid product was then washed with xylene to remove oligomer anddried at 60° C. overnight. 36.8 gm of product was obtained as a darkgreen solid which contained 31 weight percent diphenoquinone and 69weight percent tetramethylbiphenol as determined by spectrophotometricanalysis.

When the examples are repeated according to the procedure of Example 1but with the exception that the source of metal ion is changed fromdivalent copper to either of divalent nickel, cobalt or manganese ortrivalent cerium, chromium or ion, similarly satisfactory results areobtained.

In a similar manner when the starting phenol is changed from 2,6-xylenolto 2,6-di-t-butylphenol, 2,6-di-sec-butylphenol, 2-methyl-6-t-butylphenol, 2,6-dimethoxyphenol, 1-naphthol or2-t-butyl-4-methylphenol while following the procedure of Example 1,satisfactory amounts of c-c coupled products are obtained.

What is claimed is:
 1. A method of preparing by an oxidation couplingreaction a carbon-carbon coupled condensation product of an alkylphenol, an alkoxy phenol, or a 1-naphthol having one of the followingformulas: ##STR15## wherein R₂ and R₆ are alkyl, R₃ and R₅ are hydrogenor alkyl, and R₄ is hydrogen or methyl with the proviso that R₃ and R₅cannot both be tertiary alkyl, ##STR16## wherein R₂ and R₄ are alkylprovided that at least one of said alkyl groups is a tertiary alkyl andR₃ and R₅ are hydrogen or alkyl, ##STR17## wherein each R is any alkylgroup as defined above for the alkylphenols or OR, OR being alkoxy of1-6 carbon atoms, and R₁ is either hydrogen or methyl, provided that thesubstituents adjacent to R₁ cannot both be tertiary alkyl or tertiaryalkoxy, ##STR18## wherein R₂, R₃ and R₄ are hydrogen, alkyl containingfrom 1 to 5 carbon atoms, or alkoxy containing from 1 to 6 carbon atoms,provided that either or both R₂ and R₄ are hydrogen and R₅, R₆, R₇, andR₈ are hydrogen, alkyl containing from 1 to 5 carbon atoms or alkoxycontaining from 1 to 6 carbon atoms provided that tertiary alkyl ortertiary alkoxy groups may not be attached to adjacent carbon atoms ofthe naphthalene molecule, ##STR19## wherein R₃ is hydrogen, a primary,secondary or tertiary alkyl or an alkoxy group, R₅ is a primary orsecondary alkyl group containing from 1-5 carbon atoms and R₂ and R₆ area primary, secondary or tertiary alkyl or an alkoxy group, said methodcomprising contacting an aqueous mixture of the phenol or naphthol withoxygen or oxygen containing gas in the presence of a catalyst systemconsisting essentially of an imino acetic acid metal complex wherein themetal source is selected from the class consisting of divalent copper,divalent nickel, divalent cobalt, divalent manganese, trivalent cerium,trivalent chromium, and trivalent iron and wherein the imino acid hasthe formula

    R-N[ (CH.sub.2).sub.n CO.sub.2 H].sub.2

wherein n is 1 or 2 and R is hydrogen, alkyl, oxaalkyl, hydroxyalkyl,cycloalkyl, aryl, pyridyl or --(CH₂)_(n) CO₂ H wherein n is 1 or 2 and asufficient amount of an alkaline material selected from the groupconsisting of alkali metal hydroxides, alkali metal carbonates andalkali metal bicarbonates to maintain the pH in the range of about8.5-9.5 during the oxidative coupling reaction.
 2. A method, as claimedin claim 1, wherein the aqueous phenol mixture additionally comprises asurfactant.
 3. A method, as claimed in claim 1, wherein the surfactantis sodium lauryl sulfate and is present in an amount equal to at least0.1 mmol per 400 mmols of phenol or naphthol.
 4. A method, as claimed inclaim 1, wherein the phenol is an alkylphenol.
 5. A method, as claimedin claim 1, wherein the alkylphenol is a 2,6-dialkylphenol.
 6. A method,as claimed in claim 1, wherein the alkylphenol is 2,6-xylenol.
 7. Amethod, as claimed in claim 1, wherein the catalyst system comprises acupric iminoacetic acid complex.
 8. A method, as claimed in claim 1,wherein the amount of metal complex is equal to at least about 0.2 mmolsper mol of phenol or naphthol.
 9. A method as claimed in claim 1,wherein the imino acid has the formula HN(CH₂ CO₂ H)₂.
 10. A method, asclaimed in claim 1, wherein the imino acid has the formula N(CH₂ CO₂H)₃.
 11. A method, as claimed in claim 1, wherein the imino acid has theformula HOCH₂ CH₂ N(CH₂ CO₂ H)₂.
 12. A method, as claimed in claim 1,wherein the imino acid has the formula N(CH₂ CH₂ CO₂ H)₃.